is pointer assignment always atomic?

Is pointer assignment always atomic?

Will this always work:


struct list {
  int n;
  struct list* next;
};

struct stack {
  struct list* top;
};

thread one does:
for(;;) {
  print_list(stack->top);
  // read after write race condition for stack->top.
}

thread two does:
for(int count = 0; true; count++) {
  stack->top = new_int_list(count, stack->top);
}

Will the assignments and reads to stack->top always be atomic? Will the pointer value ever be half written or something, on some architecture?